State: No COVID-19 outbreak in Manchester, mountains
MONTPELIER — Vermont's public health commissioner on Tuesday ruled out an outbreak of the COVID-19 virus in the Manchester and mountains area.
Dr. Mark Levine, speaking at Gov. Phil Scott's twice-weekly COVID-19 briefing, said the department has interviewed and retested all 65 persons who had earlier tested positive for the virus by antigen test at Manchester Medical Center, and found all but four are not confirmed cases.
Of the 65 people who tested positive, only four persons also tested positive for the virus using a PCR genome test, he said.
The four confirmed cases are "not epidemiologically linked to each other," but make up two pairs of people, Levine said.
When combined with the results of more than 1,000 pop-up tests taken last week in Londonderry and Manchester, that works out to 1,613 persons tested or retested with a PCR test - and only five positive results, Levine said
That works out to a positive test rate consistent with the rest of the state — below 2 percent, Levine said.
"Therefore, we do not believe community transmission of COVID-19 has occurred," he said.
Levine said staff at Manchester Medical Center are cooperating with the Department of Health's investigation "and are just as concerned as we are" about the discrepancy between test results. He said the department was meeting with the U.S. Centers for Disease Control and Prevention about the discrepancy.
Levine also said there appears to be a correlation with the use of antigen tests on asymptomatic persons and the later negative PCR follow-up tests. He said the touted high specificity of the antigen test, which was approved on an emergency basis in May, was based on studies using a relatively small number of persons who were COVID-positive — not a population with a relatively low rate of infection such as Southern Vermont.
"One would not expect any of the Manchester results to be false positives," Levine said. "However, as pointed out after significant epidemiological and lab investigation it does appear these positive results do not represent true positive results. So there's something else going on that I'm pretty sure we will uncover."
But he also said there are potential complications with PCR tests, from how they are collected, stored and transported, to the manner in which they're conducted.
"There are so many steps along the way ... a number of things could have gone wrong," he said.
And he warned that there's no such thing as a 100 percent accurate test.
"Dealing with uncertainty is part and parcel of what we buy into in medicine," he said.
Messages left with Dr. Janel Kittredge-Sterling, an emergency medicine doctor and co-owner of Manchester Medical Center with her husband, Dr. Thomas Sterling, were not immediately returned Tuesday afternoon. Kittredge-Sterling has defended the clinic's handling of the tests, and its decision to alert the public a week ago, through the town of Manchester, that it had seen a high number of presumptive positives.
She has said MMC is eager to work with the Department of Health to find out if the discrepancy came from the antigen test, from handling of the PCR tests, or some other reason not yet known.
The potential of an outbreak was first reported a week ago, when, after months of collecting only negative tests results for COVID-19, Manchester Medical Center's antigen test for the virus returned positive results. By Wednesday, July 15, the number of presumptive positives had increased to 59. Pop-up test sites in Londonderry and Manchester took more than 1,000 samples. Some businesses protectively closed outright for a few days; others went back to curbside pickup.
In the meantime, the number of negative results on PCR follow-up tests continued to rise.
The antigen test looks for the presence of certain proteins that are part of the virus, while the PCR test — which stands for "polymerase chain reaction" — seeks the virus' unique genetic signature.
The antigen test's benefits are that it returns results much more quickly than the PCR test, which can take days. Its drawback is that it produces a greater number of "false negative" results — tests showing the lack of COVID-19 when it's actually present.
Levine said he had recently heard from Maine officials that they are having similar issues with antigen testing in their state. A call to a Maine Center for Disease Control spokesman was not immediately returned Tuesday.
Leaders in Manchester and Londonderry, where several of the presumptive positive test results were recorded, reacted with cautious optimism at the news.
"I understand what [Levine] is saying and I don't take exception to it," said Kevin Beattie, Londonderry's emergency management director. "By definition I can agree that it doesn't appear to be an outbreak. On the other hand I hope it's not misleading to the public that there's not any cases.'
"I think it's still a waiting game. We don't know 100 percent what's actually going on," Beattie said.
In Manchester, Town Manager John O'Keefe called it "probably the best news of the week."
"Just like everybody else we're all left still wondering" about the discrepancy between tests, O'Keefe said. "I think we'll get to the bottom of eventually but for now moving into the category of not having an outbreak is fantastic."
That said, O'Keefe recommended common sense precautions for residents and businesses, including adherence to the town's mask regulations.
"We're still in the midst of a pandemic and people should act accordingly," he said.
Asked what asymptomatic people should do if they want to be tested, Levine suggested that four to seven days after contact with a person exposed to COVID-19 would be the best time frame. "An antigen test for someone who hasn't had any symptoms and might not have exposure would have a higher false negative rate than a PCR test," he said. "If you're asymptomatic and want a test, a PCR would be preferable."
However, Levine expects antigen tests, because of their lower cost and speed, will be part of the COVID-19 public health strategy moving forward, especially among people showing symptoms.
"This doesn't mean antigen tests will be thrown away and never used again. These tests will have a role for sure," he said.
Reach Greg Sukiennik at email@example.com
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